An automated version of the operation span task.
ABSTRACT We present an easy-to-administer and automated version of a popular working memory (WM) capacity task (operation span; Ospan) that is mouse driven, scores itself, and requires little intervention on the part of the experimenter. It is shown that this version of Ospan correlates well with other measures of WM capacity and has both good internal consistency (alpha = .78) and test-retest reliability (.83). In addition, the automated version of Ospan (Aospan) was shown to load on the same factor as two other WM measures. This WM capacity factor correlated with a factor composed of fluid abilities measures. The utility of the Aospan was further demonstrated by analyzing response times (RTs) that indicated that RT measures obtained in the task accounted for additional variance in predicting fluid abilities. Our results suggest that Aospan is a reliable and valid indicator of WM capacity that can be applied to a wide array of research domains.
- SourceAvailable from: Oded MeironWorking Memory: Developmental Differences, Component Processes and Improvement Mechanisms., 01/2013: chapter 11: pages 157-174;
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ABSTRACT: We examined the moderating role of sex on the relationship between salivary cortisol and alpha-amylase (sAA) and a diverse battery of cognitive outcomes including measures of working memory capacity, executive functioning, and prospective memory in addition to a more traditional memory measure (episodic memory). The final sample for the analyses included 144 participants (34 men and 110 women). Multiple regressions were performed to test the moderating role of sex on the stress biomarker-cognition relationship. For backward counting performance, higher cortisol levels were related to worse performance in men, but not women. Higher cortisol levels were also related to lower word recall, but only in men. Finally, men, but not women, had higher switching costs in the Trail Making task as levels of sAA rose. The results provide evidence that sex moderates the stress biomarker-cognition relationship in a variety of cognitive outcomes. Although not part of the primary analysis, sAA and cortisol interacted such that increased sAA levels were only negatively related to backward counting performance when cortisol levels were low. The findings are discussed primarily in terms of biological sex differences in the stress response.Current psychology (New Brunswick, N.J.) 06/2014; 33(2):199-218. · 0.45 Impact Factor
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ABSTRACT: Non-native speakers have lower linguistic competence than native speakers, which renders their language less reliable in conveying their intentions. We suggest that expectations of lower competence lead listeners to adapt their manner of processing when they listen to non-native speakers. We propose that listeners use cognitive resources to adjust by increasing their reliance on top-down processes and extracting less information from the language of the non-native speaker. An eye-tracking study supports our proposal by showing that when following instructions by a non-native speaker, listeners make more contextually-induced interpretations. Those with relatively high working memory also increase their reliance on context to anticipate the speaker's upcoming reference, and are less likely to notice lexical errors in the non-native speech, indicating that they take less information from the speaker's language. These results contribute to our understanding of the flexibility in language processing and have implications for interactions between native and non-native speakers.Frontiers in Psychology 01/2014; 5:1546. · 2.80 Impact Factor
Copyright 2005 Psychonomic Society, Inc.498
Behavior Research Methods
2005, 37 (3), 498-505
Working memory (WM) span tasks have been shown
to predict performance in both higher order and lower
order cognitive tasks (e.g., Engle, Tuholski, Laughlin, &
Conway, 1999; Kane, Bleckley, Conway, & Engle, 2001).
Indeed, beginning with the work of Daneman and Car-
penter (1980), WM span tasks have been shown to pre-
dict everything from reading comprehension (Daneman &
Carpenter, 1980) to performance on the Stroop task (Kane
& Engle, 2003). In addition, these same measures have
been useful in predicting phenomena in a wide array of
other research domains. For instance, WM span tasks have
been shown to predict early onset Alzheimer’s (Rosen,
Bergeson, Putnam, Harwell, & Sunderland, 2002), the
ability to deal with life-event stress (Klein & Boals,
2001), and the effects of alcohol consumption (Finn, 2002;
see Unsworth, Heitz, & Engle, in press, for a review).
Several WM span tasks have been developed that fol-
low the lead of Daneman and Carpenter’s (1980) reading
span task, all of which share the requirement that the to-
be-remembered items are interspersed with some form
of distracting activity. In addition, all these tasks require
serial recall of the to-be-remembered items. What varies
from task to task is the nature of the distracting task and
that of the to-be-remembered items. Differences in the
distracting task include reading sentences (reading span;
Daneman & Carpenter, 1980), solving math problems
(operation span; Turner & Engle, 1989), counting circles
in different colors (counting span; Case, Kurland, &
Goldberg, 1982), and judging whether or not letters are
mirror images (spatial span; Shah & Miyake, 1996). Dif-
ferences in the to-be-remembered items include digits,
letters, words, shapes, and spatial locations, all of which
must be remembered in the correct order.
Although many of these measures differ in both the
type of distracting task and to-be-remembered items,
they have been shown to have good reliability and valid-
ity (Conway, Cowan, Bunting, Therriault, & Minkoff,
2002; Engle, et al., 1999) and likely reflect a common
construct. Engle et al. (1999) demonstrated that the most
popular WM span tasks load on the same factor and that
common measures of both short-term memory and fluid
intelligence load on separate factors. Furthermore, all of
these WM span tasks have shown high internal consis-
tency estimates and good test–retest reliability (e.g.,
Engle et al., 1999; Klein & Fiss, 1999; see also Waters &
Caplan, 2003). Thus, although there can be large differ-
ences in the types of materials used to assess WM span,
performance on these tasks have been shown to share a
good deal of common variance and to be reliable indica-
tors of a broader WM construct.
Despite their utility in predicting a wide range of cog-
nitive phenomena, WM span tasks require a great deal of
This work was supported by Grant F49620-00-1-131 from the Air
Force Office of Scientific Research. We are grateful to Michelle Grant,
Josh Holt, Melissa Jensen, Jessica Parsons, Tom Redick, Paul Tran, and
Liz Weldon for data collection assistance. Correspondence concerning
this article should be addressed to N. Unsworth, School of Psychology,
Georgia Institute of Technology, Atlanta, GA 30332-0170 (e-mail:
email@example.com) or to R. W. Engle, School of Psychology,
Georgia Institute of Technology, Atlanta, GA 30332-0170 (e-mail: randall.
Note—This article was accepted by the previous editor,
An automated version of the operation span task
NASH UNSWORTH and RICHARD P. HEITZ
Georgia Institute of Technology, Atlanta, Georgia
JOSEF C. SCHROCK
Maryville College, Maryville, Tennessee
RANDALL W. ENGLE
Georgia Institute of Technology, Atlanta, Georgia
We present an easy-to-administer and automated version of a popular working memory (WM) ca-
pacity task (operation span; Ospan) that is mouse driven, scores itself, and requires little intervention
on the part of the experimenter. It is shown that this version of Ospan correlates well with other mea-
sures of WM capacity and has both good internal consistency (alpha ? .78) and test–retest reliability
(.83). In addition, the automated version of Ospan (Aospan) was shown to load on the same factor as
two other WM measures. This WM capacity factor correlated with a factor composed of fluid abilities
measures. The utility of the Aospan was further demonstrated by analyzing response times (RTs) that
indicated that RT measures obtained in the task accounted for additional variance in predicting fluid
abilities. Our results suggest that Aospan is a reliable and valid indicator of WM capacity that can be
applied to a wide array of research domains.
experimenter time in terms of both running participants
and scoring their data. For instance, in the Turner and
Engle (1989) operation span task (Ospan) participants are
required to solve a series of math operations while trying
to remember a set of unrelated words. The operation–
word strings are presented one at a time, and for each
trial, participants are to read aloud and solve the math
operation and then read a word aloud. Immediately after
the participant reads the word, the experimenter presses
a key to move on to the next operation–word string. Fol-
lowing each complete set, the participant recalls the
words in the order presented. For example, a three-item
set might be:
is (8/2) ? 1 ? 1? bear
is (6 * 1) ? 2 ? 8? drill
is (10 * 2) ? 5 ? 15? job
The question marks cue participants to write down the
words in the correct order. Because the task is experi-
menter paced, it requires approximately 20 min of ex-
perimenter time to run each individual participant and
score the responses. Furthermore, because participants
are required to say each operation–word string aloud, in
order to attenuate rehearsal of the to-be-remembered
items, it is difficult to run participants in a group setting.
Thus, the current versions of some of the more popular
WM span tasks require a great deal of time in order to
collect a single score. Given that many research pro-
grams, including our own, utilize WM span tasks as a
prescreening tool to select individuals who are in the top
and bottom quartiles of a given WM span task distribu-
tion, this means that a substantial amount of time is al-
located to simply selecting participants. Another factor
is that, since much of the task relies on the experimenter,
there is considerable room for error and inconsistency.
The aim of the present study was to alleviate some of
these disadvantages by developing a version of the Ospan
task that was reliable, valid, and automated, and therefore
easily administered in field, clinical, or laboratory settings.
Given that WM span tasks are an increasingly popular tool
in a variety of research domains, it is important to have a
measure of WM capacity that is easy to administer and
can be done with large groups (see De Neys, D’Ydewalle,
Schaeken, & Vos, 2002, for similar arguments and task de-
velopment). To this end, we developed a version of Ospan
that is entirely mouse driven, paced on the basis of each in-
dividual’s time to complete the operations, that automati-
cally produces a score upon completion, and records a va-
riety of response time (RT) measures.
A total of 296 participants were recruited from the subject pool
at Georgia Institute of Technology and from the Atlanta, Georgia
community through newspaper advertisements. The participants
were between the ages of 18 and 35 and received either course
credit or monetary compensation for their participation. Seventy-
eight of these participants were randomly selected to come back to
assess the test–retest reliability of the automated Ospan (Aospan)
task. Each participant was tested individually in a laboratory ses-
sion lasting approximately 1 h.
Materials and Procedure
After giving informed consent, all the participants completed the
Turner and Engle (1989) Ospan task, a computer-administered ver-
sion of the Raven Progressive Matrices (Raven, Raven, & Court,
1998), and the Aospan task. Those 78 individuals in the retest sam-
ple completed the Aospan, along with a version of reading span
(Rspan; Daneman & Carpenter, 1980) and an abbreviated version of
the rotated blocks test from the Air Force Officer Qualifying Test
(Berger, Gupta, Berger, & Skinner, 1990). All computer-administered
tasks were written in E-Prime Version 1.0 (Schneider, Eschman, &
Ospan. The Turner and Engle (1989) Ospan task requires par-
ticipants to solve a series of math operations while trying to re-
member a set of unrelated words. The participants saw one math
operation–word string at a time, centered on a computer monitor.
For each trial, the participants were required to read aloud and solve
the math problem and then read aloud the word. Immediately after
the participant read the word, the next operation–word string was
presented. The operation–word strings were presented in sets of two
to five items. Following each complete set, the participant was in-
structed to recall the words in the order presented. Three trials of
each set size (set sizes 2–5) were presented, with the order of set
size varying randomly, so that the participants could not predict the
number of items. At recall, the participants were instructed to write
the words from the current set in the correct order. In addition, in
order to ensure that they were not trading off between solving the
operations and remembering the words, an 85% accuracy criterion
on the math operations was required for all the participants. The
participants received three sets (of set size 2) of practice. For all of
the span measures, items were scored if they were correct and in the
correct position. The score was thus the total number of correct
items in the correct position.1
Raven Progressive Matrices. The Raven is a measure of ab-
stract reasoning. This version of the Raven is computer adminis-
tered and consists of 36 individual items presented in three seg-
ments of 12 items each. Within each segment, the items are presented
in ascending order of difficulty (i.e., the easiest item is presented
first, and the hardest item is presented last). Each item consists of
a matrix of geometric patterns with the bottom-right pattern miss-
ing. The task for the participant is to select, among either six or
eight alternatives, the one that correctly completes the overall series
of patterns. Each matrix item appeared separately on the screen
along with the response alternatives. The participants used the
mouse and simply clicked on the response that they thought com-
pleted the pattern. The mouse click registered the response and
moved the program on to the next problem. The participants were
allotted 5 min to complete each segment. Thus, the task lasted for
either 15 min or as long it took to solve all 36 problems. A partici-
pant’s score was the total number of correct solutions. The partici-
pants received two practice problems.
Automated Ospan. This version of Ospan allowed the partici-
pant to complete the task independently of the experimenter. The
entire task was mouse driven and required the participant to only
click the mouse button. The practice session for this task was bro-
ken down into three sections. The first practice section was simple
letter span. A letter appeared on the screen, and the participants
were required to recall the letters in the same order in which they
were presented. In all experimental conditions, letters remained on-
screen for 800 msec. At recall, the participants saw a 4 ? 3 matrix
of letters (F, H, J, K, L, N, P, Q, R, S, T, and Y). Letters were used
500UNSWORTH, HEITZ, SCHROCK, AND ENGLE
because previous research has suggested that some of the shared
variance between span tasks that use words and a measure of higher
order cognition, such as reading comprehension, is due to word
knowledge (e.g., Engle, Nations, & Cantor, 1990). Recall consisted
of clicking the box next to the appropriate letters (no verbal re-
sponse was required) in the correct order. The recall phase was un-
timed. After recall, the computer provided feedback about the num-
ber of letters correctly recalled in the current set. Next, the participants
practiced the math portion of the task. They first saw a math opera-
tion (e.g., (1*2) ? 1 ? ?). The participants were instructed to solve
the operation as quickly as possible and then click the mouse to ad-
vance to the next screen. On the next screen a digit (e.g., 3) was pre-
sented and the participants were required to click either a “true” or
“false” box, depending on their answer. After each operation, the
participants were given accuracy feedback. The math practice served
to familiarize them with the math portion of the task as well as to
calculate how long it would take each person to solve the math op-
erations. Thus, the math practice attempted to account for individ-
ual differences in the time required to solve math operations. After
the math practice, the program calculated each individual’s mean
time required to solve the equations. This time (plus 2.5 SD) was
then used as a time limit for the math portion of the experimental
session for that individual. The participants completed 15 math op-
erations in this practice session.
In the final practice session, the participants performed both the
letter recall and math portions together, just as they would do in the
real block of trials (see Figure1). As in the Turner and Engle Ospan,
the participants first saw the math operation, and after they clicked
the mouse button indicating that they had solved it, they saw the
letter to be recalled. If the participants took more time to solve the
math operations than their average time plus 2.5 SD, the program
automatically moved on and counted that trial as an error. This
served to prevent the participants from rehearsing the letters when
they should be solving the operations. The 2.5-SD limit was based
on extensive piloting. Participants completed three practice trials
each of set size 2. After participants completed all of the practice
sessions, the program progressed to the real trials, which consisted
of three sets of each set size, with the set sizes ranging from 3 to 7.
This made for a total of 75 letters and 75 math problems. Note that
the order of set sizes was random for each participant. Set sizes
(1*2) + 1 = ?
When you have solved the math problem, click
the mouse to continue
Select the letters in the order presented. Use the blank button to fill in forgotten letters
You recalled 0 letters correctly out of 4
You made 1 math error(s) for this set of trials
Figure 1. Illustration of the automated operation span task. In the task, first a math operation is presented.
After it is solved, participants click the mouse and a digit is presented, which is judged to be either the correct or
incorrect answer to the math operation. This is followed by a letter for 800 msec. For recall, the correct letters
from the current set are selected in the correct order. After recall, feedback is presented for 2,000 msec.
ranging from 3 to 7 were used because pilot studies showed that
these set sizes produced the best distribution of scores (i.e., neither
on ceiling nor on floor). Because we wanted to only use those par-
ticipants who were attempting to solve both the math operations and
remember the letters, we imposed an 85% accuracy criterion for all
participants. Therefore, they were encouraged to keep their math
accuracy at or above 85% at all times. During recall, a percentage
in red was presented in the upper right-hand corner of the screen,
indicating the percentage of correctly solved math operations.
At the conclusion of the task, the program reported five scores to
the experimenter: Ospan score, total number correct, math errors,
speed errors, and accuracy errors. The first, Ospan score, used our
traditional absolute scoring method. This was the sum of all per-
fectly recalled sets. So, for example, if an individual correctly re-
called 3 letters in a set size of 3, 4 letters in a set size of 4, and 3 let-
ters in a set size of 5, his or her Ospan score would be 7 (3 ? 4 ?
0). The second score, “total number correct,” was the total number
of letters recalled in the correct position. Three types of errors were
reported: “Math errors” were the total number of task errors, which
was then broken down into “speed errors,” in which the participant
ran out of time in attempting to solve a given math operation, and
“accuracy errors,” in which the participant solved the math operation
incorrectly. The task took approximately 20–25 min to complete.
Rspan. In Rspan, the participants were required to read sen-
tences while trying to remember a set of unrelated letters (B, F, H,
J, L, M, Q, R, and X). For this task, the participants read a sentence
and determined whether it was sensical or nonsensical (e.g., “The
prosecutor’s dish was lost because it was not based on fact. ? M”).
Half of the sentences were sensical, whereas the other half were
nonsensical. Nonsensical sentences were made by simply changing
one word (e.g., “dish” from “case”) from an otherwise normal sen-
tence. There were 10–15 words in each sentence, and the partici-
pants were required to read the sentence aloud and indicate whether
it was sensical or nonsensical by saying either “yes” (sensical) or
“no” (nonsensical). After the participants gave their response, they
said the letter aloud. The experimenter then pressed a key to move
on to the next sentence–letter string. At recall, the participants
wrote down the letters from the current set in the correct order.
There were 3 trials of each set size, with set size ranging from 2 to
5. The same scoring procedure was used as in Ospan.
Rotated Blocks. The rotated blocks task is a paper-and-pencil
spatial reasoning task. This version was taken from a study by Kane
et al. (2004). For each item, an irregularly shaped 3-dimensional
block was presented with some angle of rotation. The participant’s
task was to select one of the five block alternatives that was the
exact same shape of the target when rotated. The participants re-
ceived 3 practice trials and then were given 8 min to complete 10
real items. The items we employed correspond to problems 332,
333, 334, 336, 337, 338, 340, 341, 342, and 344 from the full Air
Force Officer Qualifying Test.
The results are for 252 participants in the full sample
(M age ? 22.51 years, SD ? 4.75) and 78 participants in
the test–retest sample (M age ?22.08 years, SD ?4.23).
Forty-four (15% of 296) individuals were excluded from
data analysis because they failed to maintain the 85% ac-
curacy criterion on the math operations for the Aospan.2
As shown in Table 1, the results suggest that the Aospan
is significantly related to the Turner and Engle (1989)
Ospan (r ? .45, p ? .01). This correlation is similar to
other correlations between WM span measures observed
in the past. For instance, in the Engle et al. (1999) study,
the average correlation between the three WM span mea-
sures was .43, and the average correlation between the
WM measures in the Conway et al. (2002) study was .51.
In addition, Aospan shows a similar magnitude of corre-
lation with a measure of fluid abilities, as does the Turner
and Engle Ospan (.38 and .42, respectively). At a surface
level, this suggests that the Aospan is a valid indicator of
In order to assess reliability, we examined internal
consistency for the Aospan. Because there are three pre-
sentations of each set size, we combined the first pre-
sentation of each set size into one score, the second pre-
sentation of each set size into a second score, and the
final presentation into a third score. Cronbach’s alpha
was then computed on the basis of these three subscores.
The resulting alpha estimate was .78, which suggests
that the Aospan is reliable. When correcting for attenu-
ation, the correlation between the Aospan and the Turner
and Engle (1989) Ospan was .57. Together, these initial
analyses suggest that the Aospan is both a reliable and
valid indicator of WM capacity.
In order to more thoroughly test both the reliability
and validity of this measure, we randomly selected 78 of
the original participants to come back to get an estimate
of test–retest reliability. These individuals again per-
formed the Aospan, a version of the Rspan task, and a
measure of spatial reasoning. The mean lag between the
first and second testing was 13days (median lag?6 days,
ranging from 1 to 173 days). As shown in Table 2, the
test–retest sample and the full sample showed remark-
able similarity on all measures, suggesting that the test–
retest sample was representative of the full sample. Note
that Aospan Score 1 is the absolute scoring method given
by the program and Aospan Score 2 is the number of cor-
rect items in the correct position. Aospan Score 2 was
used for all of the analyses. In terms of test–retest relia-
bility, Table 3 shows that Aospan was highly reliable
across testing sessions (i.e., .83). In addition, Table 3
shows the correlations between all measures for the test–
retest sample. What is notable is that all three WM span
measures correlate moderately well with one another,
and the two reasoning measures correlate well with one
In order to explore these relations more fully, we sub-
mitted Ospan, the original testing of Aospan, Rspan,
Raven, and the Rotated Blocks test to a confirmatory
factor analysis. Here we constrained two factors, one
consisting of the three WM measures and one consisting
Correlations Between Ospan, Aospan, and Raven
Note—n ? 252.
**p ? .01.
502UNSWORTH, HEITZ, SCHROCK, AND ENGLE
of the two reasoning measures. Our goal was to assess
how well the Aospan would load on the WM factor and
to replicate a very simple model illustrating the relation
between WM capacity and general fluid intelligence
(gF) that has been demonstrated in the past (e.g., Engle
et al., 1999). Therefore, we predicted that the Aospan
would load highly on the WM capacity factor and load
as high as the other two WM measures. In addition, we
predicted that the correlation between WM capacity and
gF would be close to .60 on the basis of the magnitude
of correlation that previous studies have shown (see
Kane et al., 2004).
As shown in Figure 2, this is exactly what we found.
The Aospan loaded highly on the WM capacity factor
(.68), and this loading was similar to that for the original
Ospan and Rspan (.79 and .88, respectively). Further-
more, the correlation between the WM capacity factor
and the gF factor was .56, which is clearly consistent
with previous findings. The model fit was good [χ2(4) ?
6.40, p ? .17, RMSEA ? 0.08, NFI ? .96, CFI ? .98].
It should be noted that with a sample size of only 78, the
power of this analysis was quite low. Nevertheless, we
feel that this analysis is still informative. It showed that
all three WM measures had high significant loadings on
the WM capacity factor and that the correlation between
the two constructs was of similar magnitude, as has been
previously reported. Thus, in essence we replicated a
model that demonstrates the relation between WM ca-
pacity and gF, suggesting that the model is reliable de-
spite its low power. Furthermore, all of the fit indices
suggested that the model fit was good. Together, these
results suggest that the Aospan shares a good deal of
variance with other WM measures and that these mea-
sures are moderately related to fluid abilities.
Response Time Analysis of Aospan
As a final demonstration of the utility of the Aospan,
we present some analyses regarding the RT measures it
provides. One problem with the original span tasks was
that in many cases, the processing component and the to-
be-remembered items were presented onscreen simulta-
neously. For example, participants may see: ?is (8/2) ?
1 ?1? bearon the screen. Thus, if a measure of RT were
collected for this screen, it would be difficult to deter-
mine what portion of the overall time was due to com-
pleting the operation and what portion was due to en-
coding the word (although see Engle, Cantor, & Carullo,
1992). The Aospan has an advantage over previous ver-
sions of WM span tasks in that it collects two separate
RT measures for the processing of the operations as well
as RT measures for recall. That is, as shown in Figure 1,
RT is collected for each math processing screen (prob-
lem and answer screens, respectively) as well as for each
mouse click during the recall phase. Thus, it allows for a
more detailed analysis of RT measures than do previous
versions of the WM spans.
Here, we briefly examine the role that these RT mea-
sures play in predicting both performance on the span
Descriptive Statistics for Full and Test–Retest Samples
Aospan Score 1
Aospan Score 2
Note—Full sample N ? 252; test–retest sample n ? 78; Aospan Score 1 ? absolute scoring pro-
cedure; Aospan Score 2 ? correct items in the correct position scoring procedure; Lower Q ?
lower quartile; Upper Q ? upper quartile.
SkewKurtosis Lower QUpper Q
Correlations for the Test–Retest Sample
2. Aospan .499**
3. Retest Aospan.453**
4. Rspan .710**
6. Rotated Blocks .306**
Note—n ? 78.
*p ? .05.
**p ? .01.
tasks themselves and in predicting measures of higher
order cognition. Several recent reports have demonstrated
the utility of examining RT for both the processing com-
ponent of the WM span tasks (e.g., Bayliss, Jarrold,
Gunn, & Baddeley, 2003) and recall (e.g., Cowan et al.,
2003). In the present analyses, we examined the relation
between the two math processing screens and the recall
component to WM span accuracy and to performance on
the fluid abilities measures.
Table 5 shows the descriptive statistics for the three
RT measures. Note that all RT measures are based on the
mean of the median for each participant for the initial
testing of Aospan. In addition, note that these analyses
are based on 72 individuals due to data collection prob-
lems for 6 individuals. As shown in Table 4, all three RT
measures correlated moderately well with one another.
However, as is shown in Table 5, the RT measures corre-
lated less well with the span scores than with the fluid
ability measures. For instance, the only significant cor-
relation between the RT measures and the span scores was
moderate correlations between problem RT and Aospan
and Rspan. Neither answer RT nor recall RT correlated
with the span scores. However, all three RT measures did
correlate significantly with Raven, and two out of the
three RT measures correlated with the rotated blocks
task (albeit weakly). This suggests that the RT measures
are more related to fluid abilities than to accuracy on the
WM span tasks. In order to understand this more clearly,
we submitted all of the measures in Table 5 to an ex-
ploratory factor analysis with promax rotation. As shown
in Table 6, the results suggested a two-factor solution
(Eigenvalue for factor 1 ? 3.26, Eigenvalue for fac-
tor 2 ? 1.64), accounting for 49.97% of the variance
(note that the scree plot suggested three factors, but
when we forced three factors, the solution failed to con-
verge). The first factor shown in Table 6 is clearly a WM
span factor, and factor 2 is clearly made up of the RT
measures, with the Raven showing some crossloadings
between the two factors. In addition, the two factors cor-
related at ?.37. Thus, it seems that there is only a minor
relation between accuracy on the WM span tasks and RT
on the processing and recall components of the same
Given that the span scores are typically the only mea-
sure of WM performance that is used as a predictor of
higher order cognition, we examined the predictive util-
ity of both the span scores and the RT measures in pre-
dicting a composite measure of fluid abilities. The gF
composite is simply the average z-scores of the two fluid
ability measures. In order to determine the joint and
unique predictive utility of the accuracy and RT mea-
sures, we performed two hierarchal regression analyses.
As is shown in Table 7, together the span scores and the
RT measures accounted for approximately 35% of the
variance in the gF composite (e.g., .238 ? .114 ? .352).
Of the 35% of variance accounted for, 11% was uniquely
accounted for by the RT measures and 19% was uniquely
accounted for by the span measures. Thus, the two types
of measures only accounted for approximately 5% of
shared variance in the gF composite. If the goal of a
study is to predict as much variance in higher order cog-
nition as possible, adding the RT measures into the equa-
tion will help boost the predictive power of the span
tasks (e.g., see Cowan et al., 2003). However, if the goal
of the investigation is to understand why WM span scores
Figure2. Path model for the structural equation analysis of the
relation between working memory (WM) capacity and fluid in-
telligence. The numbers on the paths leading from the constructs
(circles) to the manifest variables (rectangles) are the loadings of
each measure on that construct. The number for the double-
headed path between the WM capacity factor and the gF factor
is the correlation between the two constructs. All paths and load-
ings are significant at the .05 confidence level. WMC ? working
memory capacity; gF ? general fluid intelligence; Ospan ? op-
eration span; Aospan ? automated operation span; Rspan ?
reading span; Raven ? Raven Progressive Matrices; RotBlk ?
Means, Standard Deviations, and Correlations
Between the Three RT Measures From Aospan
1. Problem RT3,120.78
2. Answer RT1,035.54
3. Recall RT 1,088.37
Note—n ? 72.
**p ? .01.
Correlations of RT Measures With
All Measures for the Test–Retest Sample
Note—n ? 72.
*p ? .05.
**p ? .01.
504UNSWORTH, HEITZ, SCHROCK, AND ENGLE
correlate with gF measures, it seems that examining RT
for both processing and recall offers little in terms of ex-
plaining the relation.
In this article, we presented an automated version of
the operation span task that is reliable, valid, and easily
administered in field, clinical, or laboratory settings.
The task is paced for each subject on the basis of the av-
erage time it takes that individual to solve the math op-
erations plus 2.5 SD. This allows participants to work at
their own pace on the operations but restricts them from
rehearsing by limiting the amount of time they are al-
lowed to solve the operations. At the end of each set,
participants are required to recall the letters in the cor-
rect serial order by clicking on the correct box in the
correct order. The program provides feedback on the
basis of the number of items recalled in each set as well
as cumulative accuracy on the math operations. We set
our accuracy criterion at 85% in order to ensure that par-
ticipants were not devoting all of their processing to re-
membering the letters. At the end of the task, the program
provides experimenters with two span scores: absolute
span, which is the sum of all correctly recalled set sizes,
and total correct, which is the total number of letters re-
called in the correct position. The program also reports
the number of total math errors, which can be broken
down into (1) the number of math errors in which the
participant exceeded the time he or she was allowed to
solve the math, and (2) the number of accuracy errors in
which the participant simply “solved” the math opera-
tion incorrectly. One advantage of this task is the fact
that it is entirely mouse driven and scores itself—hence,
it requires little intervention on the part of experimenter,
effectively reducing the amount of time experimenters
spend on each participant. The program also records a
variety of RT measures for the task, including RT for the
two operation screens as well as that for each mouse
click during recall.
This task was shown to be both reliable and valid. The
fact that the task correlated only moderately with the
Turner and Engle (1989) Ospan may seem like a cause
for concern. However, it is important to point out that
these are really two very different tasks, with the main
similarity being that the processing component in both
involves math operations. The tasks differ in that the to-
be-remembered stimuli are words in one and letters in
the other, the presentation of the stimuli is different, with
one involving only one screen and the other involving
three screens, as well as the fact that at recall in one task
participants must generate the items, whereas in the
other they must select the correct items from a pool of
items. Thus, the low correlation between the tasks is to
be expected to some extent, given these differences.
However, it is not the absolute magnitude of the zero-
order correlation that is crucial, but rather that the two
tasks show the same pattern of correlations with other
tasks (e.g., Bollen, 1989). Thus, an important finding is
that the automated version of the Ospan task was shown
to load on the same factor as two popular WM measures,
the original version of Ospan and Rspan in both a con-
firmatory and an exploratory factor analysis. Further-
more, in the confirmatory factor analysis, the WM fac-
tor was moderately correlated with a factor making up
two measures of spatial reasoning, replicating previous
findings in the literature (e.g., Kane et al., 2004). In ad-
dition, the automated task correlated with other WM
span measures with a similar magnitude of correlation
that has been reported previously, and the measure had a
similar magnitude of correlation with measures of fluid
abilities that has been reported previously (e.g., Engle
et al., 1999). Based on this, it can be concluded that the
Aospan taps the same underlying construct as both the
Turner and Engle Ospan and a version of Rspan, and this
construct is highly related to fluid abilities.
The utility of the Aospan was further demonstrated by
an examination of RT for both the processing and recall
components of the task. These analyses demonstrated
that although the RT measures were moderately corre-
lated with the span scores, the RT measures predicted
unique variance in a composite of fluid abilities, sug-
gesting that an examination of the RT measures in the
WM span tasks helps to boost their power in predicting
higher order cognition. This task can be obtained from
the attention and working memory lab Web site (avail-
able at http://psychology.gatech.edu/renglelab).
Exploratory Factor Analysis for All
Measures for the Test–Retest Sample
Note—n ? 72. Values less than .30 have been suppressed.
Hierarchical Multiple Regression Analyses of
WM Spans and RT Measures on gF Composite
Step 1 Ospan, Aospan, Rspan
Step 2Problem RT, answer RT, recall RT
Step 1Problem RT, answer RT, recall RT
Step 2Ospan, Aospan, Rspan
Note—n ? 72.
*p ? .05.
**p ? .01.
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1. Note that the statistical analyses were rerun using the absolute
scoring procedure, in which the span score is the sum of all perfectly re-
called sets. For both analyses, the results were virtually identical.
2. The majority of these participants’ errors were accuracy errors
(M ? 17.30, SD ? 10.08). In addition, they tended to have very low
Ospan and Raven’s scores (MOspan score?19.07, SD?8.03; MAospan
score ? 39.89, SD ? 17.28; M Raven score ? 18.84, SD ? 5.64). The
pattern and magnitude of correlations did not change when analyzing
the data with these participants included.
(Manuscript received March 16, 2004;
revision accepted for publication August 14, 2004.)
Richard Philip Heitz